Brake for vehicles



c. cHoUlNGs 2,318,756 i y BRAKE FOR VEHICLES 2Sheerts-Sheet 1 May-.11, 1943.

May 11, 1943. 1 c. cHQUlNGs 2,318,756 BRAKE FOR VEHICLES l a Filed sept. 24, 1941-` 2 sheetsnsheetvz Fig? [gli Patented May 11, 1943 BRAKE FOR VEHICLES Leslie Cyril Chouings, Leamington Spa, England, assigner to Automotive Products ompany Limited, Leamington Spa, England Application September; 24, will, Serial No. ll2,l9l in Great Britain December lit, lui@ (ci. cai-azi 3, Claims.

l'This invention relates to brakes for vehicles and more specifically to brake operating mech-V anism of the kind comprising a liquid pressure actuated piston constituting a common operating member and, coupled to thefbrakes on a pluraiity of wheels7 a pedal or equivalent driveroperated control and a valve. device operated by the pedal or equivalent to restrict the normally free circulation of liquid from a pump driven by the vehicle transmission and thereby to create liquid pressure to act on the common operatingmember and apply the brakes, thefvalve device being interposed' between the pedal or equivalent andthe piston so that pressure on the pedal or equivalent is adapted to be transmitted directly through the valve device to the piston, the valve beingv so arranged that it tends to re-o'pen under the pressure of the liquid to limit such pressure in accordance with the pressure applied to the pedal 'or equivalent.v

According to the present invention', al longitudinally apertured plunger Y'co-amai with the piston and mounted in a housing is interposed i between the piston and a thrust member con nected to the pedal or equivalent, a port in the housing on the side of the plunger nearer the piston being connected to the pump and au outlet port being provided in the housing at the opposite side of the plunger andthe aperture in the plunger is restricted hy operation of the pedal or equivalent to apply thrust through the plunger to the piston, whereby pressure is built up to actuatethe piston hydraulically.

According to anotheraspect of the invention'.

a longitudinally apertured plunger forms a movable transverse partition dividing into two chambers e, housing co-axial with the piston, the aperture in the plunger being restricted by operation of the pedal or equivalent to. apply thrust through trie plungerto the piston, to restrict fthe new 'of liquid delivered to the chamber adieeent the piston from that chamber to the cham er on the opposite side oi the plunger and thereby 'to puliti up pressure to actuate the piston hydraulically. y

The aperture in the plunger may he restricted oy a closure member formed on a spigot integral with the piston, or by an auxiliary plunger inter-s posed between the main plunger and the pedaloperated thrust member and the plunger may j he formed `with s countersunlr. recess et one entil of the aperture therethrough to co-operate with A connectingpassage end portion of equal diameterv to the intermediate portion and separated therefrom by an annular recess, and a forwardly projecting portion also of smaller diameter thanthe -intermediate portion. The aperture through thev plunger may comprise an axial passageextending from the forward end thereof to a point beyond the intermediate rtion where it is intersected by a diametral passage opening into the annular recess. f y

may be provided between the annular recess in the plunger and the space between the plunger and, the piston, a nonreturn valve in said connecting passage being arranged totpermit the ow of liquid from the annular recess-but not in, the opposite direction. Ihe invention is hereinafter described with reference to the accompanying drawings in ldiagremnnatically; and

e frusto-conicai'closure member,` The plunger may have an intermediate portion winch is a the here o the housing, e

Figures 2 and 3 are sectional elevations of mod ified forms of praise operating mechanism according to the invention.

In the form of the invention shown in Figure l, a piston i3 constituting the eon'gmon operating member is formed integral with the piston ii of e liquid pressure master cylinder il? ci known type. the said master cylinder l2 heini." connected 'to wheel cylinders i3 on tlievarions brakes by means oi piping ld. The pressure receiving piston ii is slidalole in 'the .rear end of the master cylinder l2. From the rear end of the master cylinder lthere extends a yz-lai cylinder iti of smaller diameter attached in e Huid-tight manner to the master cylinder and in this cylinder i5 is slidably mounted c plunger it having an intermediate portion il' which is a sliding fit in the cylinder and *tens it; and i@ of reduced diameter oneacrf si vof such( intermediate portion, the Arear end oi t plunger. that is the end remote from the pistol,

tu, losing formed with afiurther enlarged I1, where it is intersected by a diametral passage 29 opening into the space 3| around the reduced portion I9 of the plunger. The open end of the axial passage 28 is ared or countersunk as at 32 to provide a valve seat' and the piston IIJ is formed with a valve 33 having a frustoconical end 34 adapted to engage the valve seat 32 and close the passage through the plunger.

The rear end of the plunger is deeply recessed at 35 to receive a push-rod 36 connected to a foot-pedal 31 operable by the driver of the vehicle. The valve 33 on the piston I Il is recessed axially to a considerable depth at 38 to receive a spring 39'acting to urge' the piston I0 and plunger I6 apart. The spring 39 acts on a cupshaped member 4| having its sides slotted to form axially extending fingers 42, the ends of which engage with an internal shoulder 43 at the inner edge of the valve seat 32 on the plunger I6 sothat the spring tends to force the plunger away from the piston. A bolt 44 passing through the cup 4| and the spring 39 is screwedinto a threaded bore 45 at the end of the recess in the piston, the head 46 of the bolt engaging thebase of the cup to limit its movement out of" the.

recess.

In the inoperative position of the parts, the piston unit I0, II is held against a stop v41 by the usual return spring 46 in the master cylinder I2 and the plunger I6 is in turn urged against a stop ring 49 in the rear end of the cylinder I by the spring 39. The liquid delivered by the pump 26 therefore ilows between the conical end 34 of the valve and the valve face 32, through the slots in the `cup-shaped member 4| and through the passages 28and 29 in the plunger to the outlet port 24, no substantial restriction of its passage taking place so that the flow is substantially free and no pressure is built up. When the pedal 31 is depressed, the plunger I6 approaches the piston I0 and the now of liquid between the plunger and valve is restricted, so that pressure is built up between the piston I0 and the intermediate enlarged portion I1 of the plunger I6. This pressure actsboth to urge the piston I 0 forwardly to apply the brakesoand to urge the plunger I 6 backwardly against the pressure on the pedal, but as the piston III has a larger area than the plunger I6 a greater totall pressure is exerted on the former, a proportional but smaller reaction being transmitted through the plunger to the pedal. It will be evident' that with any given pressure on the pedal 31 the4 liquid pressure will build up to a corresponding limit at which the valve is held open just suiiiciently to permit liquid to escape at the same rate as it is delivered by the pump. The degree of braking obtained is thus completely under the control of the driver and the driver can feel,

the degree of braking applied. The removal of pressure from the brake pedal allows the plunger to return and permits the wide opening of the valve so that the liquid pressure is released and the pistonY Ill returns to its normal position, thus releasing the brakes. When thepumpv is not operating, the pedal pressure is transmitted di-k rectly through the plunger I6 to the piston III,

'59 co-operating with 66 immediately behind the frusto-conical face of the valve 33 on the piston I0 coming into engagement with the valve face 32 on the plunger I 6 and the master cylinder is operated to apply the brakes, even if the pump has failed.

In the form of the invention shown iny Figure 2 the piston `|0 forming the common operating member is again integral with the piston of a liquid pressure master 'cylinder I2 and the cylinder 5I in which the plunger 52 is mounted is reduced in internal `iameter at its end adjament the cylinder I2. e plunger 52 is in the form of a hollow stem 53 with a head 54 formed on its end remote from the'piston I0, th'e stem 53 being a sliding flt in the reduced portion of the cylinder 5|. The plunger head 54 is formed with a frusto-conical recess 55 into which the passage 56 through the stem opens, and an auxiliary plunger 51, arranged between the plunger head and a push rod 58 operated by the brake pedal, is formed with a frusto-conical projection the recess 55 to form a valve. Fluid from the pump enters the cylinder by a port 6| leading to a counterbored recess 62 at the end of the reduced portion of the cylinder 5| nearer to the piston I 0 and the outlet porty so that liquid flowing from one to the other must i pass through passage 56 in the plunger and its flow can," therefore, be controlled by the valve. The end of the plunger stem 53 abuts the piston I0 to provide direct mechanical operation of the piston if the pump should not be delivering liquid.

The arrangement shown in Figure 3 closely resembles that shown in Figure 1, but the return spring 39 for the plunger I6 is omitted, the pressure of the liquid being relied upon to return the plunger into contact with its stop ring 49. A passage 65 connects the space 3| to the space the piston I6 and a nonretum valve 61 in the passage 65 permits liquid to ow from the space 3| into the space 66 but not in the opposite direction. The space 3| is connected to the reservoir through a port 6l.

If the brakes are applied suddenly, the plunger |6 and piston I 0 may be moved forward so rapidly that the pump will not deliver sulcient iluid to keep the space 66 full, as this space is increasing in volume due to the difference in diameter between the cylinders I2 and I5. The provision of the passage 65 enables liquid to flow from the space 3| toV keep the space 66 full and consequently the liquid pressure commences to build up on the piston I9 as soon as the rate of forward movement of the piston and plunger de-l creases suilciently, instead of beingdelayed by y the need for filling upthe increased volume of the space 66. l

The piston I0 mayin any o1' the above arrangements, be coupled to a thrust member operating the brakes through mechanical linkage instead of being coupled a liquid pressure master cylinder.

What I laimis:

1. Brake operating mechanism for vehicles comprising brakes on at least some of the wheels of the vehicle, a common operating member for the housing forward of and apply the brakes,

4the said brakes comprising in which said piston is mounted, driver operatedy the intermediate portion, a reduced portion forming an annular recess between the two portions fitting in the bore,` and a forwardly projecting reduced portion, a pump driven from the vehicle transmission, a connection from said pump to the intermediate portion of the plunger, a reservoir, a connection from said reservoir to the annular recesslaround the plunger, a passage through said plunger connecting the spaces surrounding the two reduced portions of the plunger, a seat in said passage, and

a valve member integral with said piston adapted to approach said seat when the thrust member is operated to apply thrust to the piston and thereby to build up pressure to act on said piston the presssure so built up acting on the piston and plunger in opposite directions so as to tend to separate them and reg lieve the pressure.

2. Brake operating mechanism for vehiclescomprising, brakes on at least some of the wheels of the vehicle, a common operating member for a piston, a cylinder thrust means for moving said piston to apply the brakes, a housing fixed to and co-axial with said diametral passage a plunger in said cylinder, a uniform bore through said housing. housing and interposed between said piston and said thrust means, an annular recess formed by a reduced portion of the plunger adjacentthe rear end thereof, a pump driven from the vehicle transmission, a connection from the pump to said housing in front of the plunger, a reservoir, a connection from said reservoir to the annular recess, an axial passage in said plunger extending from the forward end thereof to the recessed part of the plunger, a connecting said axial passage tothe annular recess, a seat at the forward end of the passage, and a valve member integral with the piston adapted at times to engagey said seat'l to build up pressure to act on the piston and apply the brakes.

3. Brake loperating mechanism, according to claim 2, wherein passage other than the passage through the p ger controlled by the valve member is providedbetween the pump connec-` tion and the reservoir connection to the housing.

and a non-return valve is provided in said passage to permit flow of liquid only from said reservoir connection to said pump connection.

LESLIE CYRIL CHOUINGS. 

